In general, the luminance of an organic EL element depends on a drive current supplied to the element. The light emission luminance of the element increases in proportion to the drive current. Accordingly, the power consumption of a display including organic EL elements is determined by an average display luminance. In other words, unlike a liquid crystal display, the power consumption of the organic EL display significantly varies depending on the display image. For example, the organic EL display consumes the greatest amount of power when displaying an absolute white image, whereas the organic EL display consumes power of approximately 20% to 40% of the power required for the absolute white image when displaying a general natural image.
However, a power circuit capacity and a battery capacity are designed in view of a case where the display consumes the greatest amount of power. Hence, the amount of power consumption that is three to four times as high as that required for a general natural image has to be taken into consideration. This hinders reduction of power consumption of devices and downsizing of the devices.
In view of this, there is a conventional technique which reduces power consumption with little decrease in display luminance (for example, see PTL 1). In the technique, the reduction is achieved by detecting a peak value of video data, adjusting the cathode voltage of an organic EL element based on the detected data only when a driving transistor which drives the organic EL element operates in a saturated region, and decreasing a drive voltage supplied to a display.